This is the thoroughly revised and updated sample question paper in Physics XII-2014 specially prepared for the students appearing in the class XII final exams 2014. The questions are specially prepared covering the whole syllabus.

(Answer all the questions . Your answers should be brief and to the point).

Q1. A magnet is moving towards a coil with a uniform speed υ as shown in the figure. State the direction of the induced current in the resistor R.

Ans 1. From X to Y.

Q2. Give one example each of a ‘system’ that uses the (i) Sky wave (ii) Space wave mode of propagation 1.

Q3. A concave mirror, of aperture (an opening, hole) 4cm, has a point object placed on its principal axis (main axis) at a distance of 10cm from the mirror. The image, formed by the mirror (actual image) is not a sharp image. Give reasons.

Ans 3. The incident rays are not paraxial.

Q4. Two dipoles, made from charges ±q and ±Q, respectively, have equal dipole moments. Give the (i) ratio between the ‘separations’ of the these two pairs of charges (ii) angle between the dipole axis of these two dipoles.

Ans 4. As qa = Qa’, we have a’/a= q/Q and θ = 0°.

Q5. Define the term ‘Transducer’ for a communication system.

Ans 5. A ‘transducer’ is any device that converts one form of energy into another.

Q6. For the circuit shown here, would the balancing length increase, 2 decrease or remain the same, if (i) R1 is decreased (ii) R2 is increased without any other change, (in each case) in the restof the circuit. Justify your answers in each case.

Fig.

Ans 6. (i) decreases (The potential gradient would increase).

(ii) increases (The terminal p.d across the cell would increase).

Q7. An athlete peddles a stationary tricycle whose pedals are attached to a coil having 100 turns each of area 0.1m². The coil, lying in the X-Y plane, is rotated, in this plane, at the rate of 50 rpm, about the Y-axis region where a uniform magnetic field, B ̅̅̅̅̅̂̂= (0.01)k tesla is present. Find the following:

(i) maximum emf (ii) average e.m.f which is generated in the coil after one complete revolution.

Ans 7. (i) The maximum emf ‘ε’ generated in the coil is,

ε = N B A ω.

= N B A 2Πf

= [100 x 0.01 x 0.1 x 2Π(5/6) ] V

= (Π/6)V≈ 0.52 V

(ii) The average emf generated in the coil after one complete revolution will be = 0.

Q8. A monochromatic source, emitting light of wave length (λ) 600 nm has a power output of 66W. Calculate the number of photons emitted by this source in 2 minutes.

Q9. The galvanometer in the given figure does not show any deflection. Calculate the ratio of the resistors R1 and R2 used in these two circuits.

Fig.

Ans 9. For circuit 1 we have (from the Wheatstone

bridge balance condition), R1/9 = 4/6. R1 = 6Ω In circuit 2, the interchange of the positions of the battery and the galvanometer (sensitive ammeter) does not change the balance condition (it will not effect the diagram in any manner)

R2/8 = 6/12.

Q10. The electron in an hydrogen atom initially in a state of quantum number makes a transition (changes its state) to a state whose excitation energy (excited state* )with respect to the ground state is 10.2 eV. If the wavelength associated with the photon (light particles) emitted in this transition are 487.5 mm, find the: (i) energy in eV (ii) value of the quantum number n1 of the electron in its initial state.

Ans 10. In an hydrogen atom the energy (En) of electron in a state having principal quantum number ‘n’ is given by: